package com.sunny.l54;

/**
 * @Author zsunny
 * @Date 2018/9/13 9:26
 * @Mail zsunny@yeah.net
 */
public class Solution {

    public static void main(String[] args) {
        Solution solution = new Solution();
        System.out.println(solution.numTrees(3));
    }

    public int numTrees(int n) {
        if(n <= 1)
            return 1;
        int[] dp = new int[n+1];
        dp[0] = dp[1] = 1;
        for(int i=2;i<=n;i++){
            for(int j=0;j<i;j++){
                dp[i] += dp[j]*dp[i-j-1];
            }
        }
        return dp[n];
    }

}
